What is it about?
Pregnancy is known to be followed by a certain degree of insulin resistance. It is well known that in type 1 diabetes insulin requirements increase during the third trimester. A recent study in nonpregnant transgenic mice revealed that hPGH causes insulin resistance at levels somewhat above human third trimester levels. Diabetes in pregnancy may lead to macrosomia in the newborn, but the impact of hPGH on birth weight in diabetes, especially type 1 diabetes, has only been sparsely investigated. In contrast, both IGF-I and IGF-II have been found to be correlated to birth weight in diabetic, as well as in normal, pregnancies, although not consistently. Thus, as hPGH may theoretically influence both fetal growth and maternal insulin requirements in type 1 diabetes, this study was undertaken with the aim of examining the relationship between hPGH and IGF-I and -II in a cohort of type 1 diabetic subjects and to examine the impact of hPGH and IGFs on birth weight and placental weight. Furthermore, the extent to which insulin requirements in pregnancy were related to hPGH levels was examined.
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Why is it important?
In pregnancy, human placental GH (hPGH) gradually replaces pituitary GH. From wk 20 onward, GH is only found in minute amounts, whereas hPGH levels steadily increase until approximately wk 35, whereafter a slight decrease is observed. Due to its structural similarity with GH, hPGH is supposed to convey similar effects. As hPGH is found only in maternal blood, hPGH is supposed to be involved in regulation of the availability of nutrients to the placenta. hPGH may influence the fetal substrate supply either directly via autocrine and paracrine mechanisms or via IGF-I, which it regulates. In support of an effect on fetal growth, lower maternal levels ofhPGHhave been found in pregnancies complicated by intrauterine growth retardation, and hPGH has been found to be positively correlated to birth weight
Perspectives
Our study points toward an effect of hPGH on fetal growth in pregnancies in type 1 diabetic subjects. Furthermore, effects of GHs on IGF-I are suggested both during the shift from pituitary to placental GH and during the hPGH-dominated third trimester of pregnancy. In contrast, a direct diabetogenic effect of hPGH was not supported by the present findings.
Dr Finn Friis Lauszus
Herning hospital
Read the Original
This page is a summary of: Human Placental Growth Hormone, Insulin-Like Growth Factor I and -II, and Insulin Requirements during Pregnancy in Type 1 Diabetes, The Journal of Clinical Endocrinology & Metabolism, September 2003, Endocrine Society,
DOI: 10.1210/jc.2003-030726.
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